Heat storage cooker

ABSTRACT

A heat storage cooker comprising a least one oven cavity formed by walls of cast iron, and at least one electric radiant heating element which is in thermal contact with at least one wall such that in use the electric radiant heating element transfers heat energy to the wall which subsequently radiates at least part of that heat energy in to the oven cavity. Two or more ovens may be provided, each one with its own radiant heating element.

This invention relates to domestic cookers of the heat-storage type.

It is known to provide cookers including at least one oven compartmentwhich comprises a box of relatively thin steel sheets surrounded bythermal insulation or air. A heating element may be provided within thebox, such as a gas burner, or within the walls themselves, such as thinelectric heating elements. To help ensure that the oven is at the sameelevated temperature at all locations a fan is often provided whichblows air around inside the compartment. The walls of the oven storevery little heat and so the cavity can be warmed up to full operatingtemperature from cold very quickly. Conversely when the heat source isturned off they cool down very quickly as well.

It is also known to provide domestic cookers which are known asheat-storage type cookers. Perhaps the most well known and loved are theapplicants own Aga and Rayburn Ranges of heat storage cookers. Thesecookers differ from the pressed steel type because the oven walls areformed of a thick material with high specific heat capacity so that thewalls have a relatively high thermal mass. The cavity does not contain aheating element, and the walls also are not provided with a directheating element. Instead the one or more ovens are in thermal contactwith a system of ducts communicating with a combustion chamber whichserves as heat source.

The combustion chamber is fed with a solid fuel, or, and more commonlynowadays, with fuels such as kerosene, natural gas or propane. By makingthe shell from cast iron, heat from the heat source is stored residuallyallowing the device to provide constant high temperatures with heatsource constantly topping it up if heat is lost (for instance by openinga door to the oven).

It is also known to provide a heat storage stove with the heat exchangechamber containing one or more resistance heating elements. Two types ofelectric heat store stoves have been proposed. In the first the heatstore is “charged” with heat to a high level using a high power heatingelement rated at 30 amps at 240 volts. This charging can be performedovernight when electricity is cheaper and then released from the storeduring the day as required to keep the stove at its operatingtemperature.

Because it takes a long time to heat up the cookers are usually left onfor extended periods so they are ready to use at meal times. This styleof cooking is very different to cooking with a sheet steel cooker, andmany people feel that food cooked in a range cooker is preferable. Abeneficial side effect of the heat stored in the cast iron is that agentle background heat is emitted constantly which gives the room inwhich it is located a cozy warm feel. A potential disadvantage of thistype of cooker over the pressed steel cookers is the long warm up cyclefor the ovens.

According to a first aspect the invention provides a heat storage cookercomprising a least one oven cavity formed by walls of high thermal mass,such as cast iron, and at least one electric radiant heating elementwhich is embedded in at least one of the walls such that in use theelectric radiant heating element transfers heat energy to the wall whichsubsequently radiates at least part of that heat energy in to the ovencavity.

By walls of high thermal mass we mean walls which are made of cast ironor similar and are relatively thick so that they retain heat in themanner of a traditional heat storage oven for gradual release over anextended period of time. For instance using cast iron for the walls ofthe oven cavity it is ensured that the ovens cook using radiant heat inthe same manner as a traditional heat storage cooker. However, becausethe total amount of thermal mass is lower than a traditional cooker ofthat type and heat is applied directly to each oven using a radiantheating element thermally connected to a wall of the oven rather than asingle heat source connected to all the ovens through a series of ductsthe warm up time is much reduced, and an increase in efficiency may beattained. At the same time the traditional comforting effect of gentleheat radiated out of the cooker from the heat stored in the cast ironwalls is retained compared with a steel walled cooker.

The or each radiant heating element may comprise a radiant hot plate.Each element may comprise a generally flat plate of ceramic or glassceramic covering a coil of electrical resistive heating element. Aspacer may be provided to make the ceramic plate stand proud of theheating element, and a backing plate—perhaps of thin pressed steel, maybe provided to enclose the heating element. An optional thermalinsulated may be provided between the coil and the backing plate. One ormore holes may be provided through which bolts can pass to bolt the heatsource to a wall of the oven cavity. A thermocouple may be providedwithin the element which may output a signal that can be used to helpcontrol the temperature of the element.

More preferably each radiant heating element may comprise a commercialgrade solid element hot plate or radiant heating element in which theelectrical heating element—either a coil or ribbon—is embedded in aplate like cast iron body. This arrangement ensures excellent evenradiate heat distribution and also enables high levels of heat transferfrom the body to the wall which it is secured to. A seal may be providedbetween the element and the body. The cast iron body effectively forms apart of the wall of the oven cavity so that the heating element isembedded in the wall, causing the iron to heat up and store the heat.

The hot plate may be located inside the cavity in thermal contact withan inner face of the wall. In this way it will radiate heat directlyinto the cavity, some of which will heat the walls of the cavity, andalso heat the wall it contacts through conduction.

Where it is located inside the cavity, the hot plate may be located in arecess in respective wall of the oven cavity so that the surface of thehot plate may be substantially flush with the surrounding surface of thewall.

The area of the hot plate may be at least 50 percent of the area of theassociated oven wall.

The wall may have a thickness of at least 3 mm, and preferably at least5 mm, and may be of cast iron. The or each wall may form part of a castiron frame which defines more than one oven cavity.

Therefore more than one cavity may be provided, each one comprisingwalls of high thermal mass, and at least one radiant heating element(such as an electric hot plate) which is in thermal contact with atleast one of the walls to form an integral part of the wall such that inuse the electric hot plate transfers heat energy to the wall whichsubsequently radiates at least part of that heat energy in to the ovencavity.

There may preferably be two oven cavities or three cavities. One of theovens may be provided with more radiant heat elements than the other toenable it to attain a higher temperature than the other. For instanceone may include two elements and the others only one.

Each wall of a cavity may be separate from any other wall and secured sothat it is in thermal contact with at least one other wall of thecavity. Alternatively two or more walls may be integrally formed. Ifcast iron is used, two or more walls may be formed as part of a singlecasting.

A hot plate may be secured to a wall of a cavity using one or more boltsor screws. A thermal matching paste may be provided between the hotplate and the wall.

Each hot plate may be arranged to radiate heat substantially evenly overthe whole of its surface, by which we mean all points radiate at atemperate within 20 percent, or 10 percent, or 5 percent of thetemperature of any other point on the surface. This ensures heat isradiated evenly into the cavity (where it is located inside) and alsointo the cast iron wall avoiding undesirable hot spots.

Each hot plate may be constructed generally of the same material as thewall it is secured to, typically cast iron, so that when a steady statetemperature is reached in the oven the walls and hot plate will begenerally at the same temperature. When the oven is switched off andallowed to cool it will do so slowly due to the high thermal mass of thewalls and also the hot plate. To further help retain heat in thecavities an amount of thermal insulation may be packed around thecavities.

A controller may be provided which controls the heating of the heatingelements. Where two oven cavities are present, the controller mayinclude a setting which maintains a first one of the ovens at a firstset temperature when the cooker is switched on a second one of the ovensat a second set temperature when the cooker is switched on, the secondtemperature being lower than the first. The controller may include apreset strategy which raises the ovens to these temperatures andmaintains them there at a single command from a user. These temperaturesmay be permanently stored in a memory associated with the controller. Abutton, rotary knob, switch or other input may be provided which a usercan operate to initiate this strategy or to turn off the oven whenheating is not needed.

Providing two preset temperatures allows the cooker to mimic thedifferent temperatures of a traditional cast iron heat storage rangecooker, in which a single heat source is provided that heats all theovens and so does not allow independent control.

Where three ovens are provided, three different preset temperatures maybe stored in the memory of the controller. One of these may be atemperature far below the other two to allow the oven to be used as awarming oven. The three preset temperatures are preferably approximately240° C., 180° C. & 120° C.

The controller may receive input signals from a thermocouple associatedwith the or each heating element associated with a cavity, the or eachthermocouple providing an output indicative of the temperature of aheating element, and also from a thermocouple that measures the overalltemperature inside an oven cavity.

The controller may allow the user to override the preset temperatures sothat individual control of the temperature of each oven may be achieved.A separate switch, button, rotary knob or other input may be providedwhich a user can operate to provide an indication of the desiredtemperature of an oven to the controller, for example to choose one ofthree preset temperatures.

The controller may, for instance, include or otherwise be compatiblewith a controller of the kind disclosed in GB2447777, in which aprogrammable timer is provided for control of the operation of atraditional heat storage oven. The principles disclosed there for thecontrol of a set of ovens from a common heat source apply equally to thecontrol of the individual heat elements of the present invention.

Hot plates are well known for use as a heated surface on which to cookfood items, often forming part of the hob of a cooker. It is not knownto use them to heat an oven cavity and not known to use them to heat acast iron wall of an oven to provide an effect similar to traditionalheat storage cooker. There are a wide variety of different typesavailable, and the preferred type for use in this invention comprises asandwich construction with two layers of cast iron or ceramic material(or indeed any other material of high thermal mass) surrounding one ormore flat electrical heating elements.

The cooker may include a hob which is provided with at least two hotplates, each one covered by an insulated lid. The hot plates may becircular to enable the hot plate to be styled in the manner of atraditional heat storage cooker.

The cooker may be absent any form of central heat source, traditionallya heating barrel, and as such may also be absent the ducts that wouldotherwise be needed to take the heat from the central heat source toeach oven cavity. The controller may be located in the space that wouldtraditionally have been occupied by the central heat source.

According to a second aspect the invention provides a heat storagecooker comprising at least two oven cavities, each one formed from aplurality of walls having a high thermal mass and each one beingprovided with a respective heat source which is adapted to heat thewalls of the oven cavity which in turn heat the interior of the cavityby radiating heat.

Each oven cavity may be heated independently of the other. The walls ofone of the oven cavities may be insulated from the walls of the othercavity, or one or more walls of one cavity may be in good thermalcontact with one or more walls of the other cavity.

Each oven may function independently as a heat storage device, meaningthat the thermal mass of the walls of the oven is sufficient that itretains heat for an extended period of time to continue to heat the ovencavity.

The heat source of each oven may comprise a hot plate or otherelectrical heating element in thermal contact with at least one wall ofthe oven cavity. The heat source may comprise a hot plate. The walls maycomprise cast iron components.

A controller may be provided, which may operate according to theprinciples set out for the controller of the first aspect of theinvention. Indeed, any of the features of the first aspect of theinvention may be incorporated into the second aspect of the invention.

There will now be described, by way of example only, one embodiment ofthe present invention with reference to the accompanying drawings ofwhich:

FIG. 1 is a general view of an embodiment of a domestic heat storagecooker in accordance with the present invention;

FIG. 2 is an exploded view of the parts of one of the oven cavities ofthe cooker;

FIG. 3 is a schematic view of the control circuit and heating elementsof the cooker of FIGS. 1 and 2; and

FIG. 4 is a view of the user interface device that forms part of acontroller for the cooker.

A range cooker 1 for domestic use is shown in FIG. 1 of the drawings. Itcomprises a shell comprising front, side, rear and base panels (althoughonly the front is shown) bolted and screwed to a support frame (notshown). The front panel 2 is about 120 cm wide in this example, althoughit may be wider or narrower, and is located above a plinth 3. It can bestyled in a variety of different manners depending on whether atraditional or contemporize effect is required, and also can be providedin a range of different colours. It is provided with three openingswhich are covered by respective hinged insulated doors 4, 5, 6. Eachdoor is provided with a handle 4 a, 5 a, 6 a to enable the door to beopened and closed. The top panel 7 forms a hob, and is inset with twocircular hot plates. Each hot plate is covered by a hinged insulated lid8,9, again each hinged lid being provided with a grab handle. Whenlowered, the lids 8,9 retain heat in the hot plates when they areswitched off. Each hot plate is supplied with electricity through wiresconnected to respective outputs of a controller, as described later.

Inside the frame are three oven cavities. The doors of FIG. 1 show thegeneral location of the three oven cavities and their generalconstruction.

A view of the walls of one of the cavities (the other is to beunderstood to be of similar construction) is provided in FIG. 2 of thedrawings. Each cavity comprises a base, a rear wall, two side walls anda top wall. The front wall of each cavity is open and aligned with arespective opening in the front panel of the range cooker, allowingaccess to the cavities through the doors 4,5,6.

The walls (including the top and bottom walls) of each oven comprisecast iron plates of around 5 mm thickness, giving them a high thermalmass. The walls meet one another in such a manner that each oven cavitydefines a closed spaced when the doors are shut and that heat canreadily conduct from one wall into the adjacent wall or walls. Indeed ifpreferred the walls may be cast as one part, with two or more wallsbeing integrally connected. Each oven is individually insulated. Thermalinsulation is provided between the walls and the shell to stop the shellfrom becoming too hot to comfortably touch but also to minimise unwantedheat loss from the cast iron walls, ensuring they cool down only slowly.

The upper right oven cavity, when viewed from the front, is intended foruse as a roasting and baking oven and as such operates at highertemperature than the bottom right oven cavity. In this embodiment all ofthe ovens are the same size.

Secured to at least one wall of each oven is a rectangular or square hotplate or radiant heating element 20 as shown in FIG. 2 which is inthermal contact with the cast iron wall. A matching paste may beprovided between them to improve conductivity from one to the other. Thehot plate is located on the side of the oven wall that is internal tothe oven cavity, although it could be located on the other side of thewall. In this example five such hot plates are used, two for the hob andone in each oven. There are five fixed temperature cooking zones on thecooker-three ovens and two hotplates.

-   -   Zone 1_hot spot_(—)330° C._single plate 2.5 kW    -   Zone 2_simmer spot_(—)220° C._single plate 2.5 kW    -   Zone 3_roast oven_(—)240° C._dual plates 2.5 kW each (run at 2:1        power ratio top element to bottom element)    -   Zone 4_baking oven_(—)185° C._dual plates 2.5 kW each (run at        2:1 power ratio top element to bottom element)    -   Zone 5_simmer oven_(—)120° C._single plate 2.5 kW (run at a        maximum of 50% power—i.e. 1.25 kW)

Each one receives electricity from the controller. Each one comprises aheating element embedded in a thermal compound within a plate of castiron material. The arrangement ensures that the element radiates heatevenly preventing hot spots forming in the oven. Also because thematerial of the hot plate matches that of the walls once it has beenheated to a steady state temperature the hot plate and walls willgenerally all be at a similar temperature, and when switched off willall cool at the same rate and remain at the same temperature.

Located behind a door 11 at the upper left front of the cooker is acontroller 10 which includes a user interface panel with a set ofbuttons which enable the hot plates on the hob to be turned on and offand to be set at different heat outputs. The buttons also turn on andoff the ovens. Each button is connected to the controller which respondsto changes in the position of the knobs. This panel can be seen in FIG.4 of the drawings and is described in more detail later.

The electrical diagram for the cooker is shown schematically in FIG. 3of the accompanying drawings. The control system can be separated intothree parts. It comprises a Main power board which is provided with highpower electrical switches, in this example relays and triacs, forselectively connecting each heat element to the mains electricitysupply.

The switches are controlled by a secondary printed circuit board in theform of a control panel which contains switches allowing the user tochoose between auto and manual operation, selecting the required cookzones and operate the oven vent fan. This may be located behind the topleft door of the cooker. The panel also receives inputs fromthermocouples associated with each cooking zone. The secondary printedcircuit board carries the controller that determines the switch statesrequired and is connected to a memory in which is stored a presettemperature for the top oven and the bottom oven. The preset temperaturefor the top oven is higher than for the bottom oven.

Starting with all the ovens turned off, all the switches are arranged sothat all the radiant heat elements are isolated from the mains supply.As soon as the ovens are turned on by movement of the associated buttonthe controller applies full power to all the hotplates that form a partof the oven walls by changing the state of the switches to connect thehotplates to the mains supply. This causes the ovens to rapidly heat,all the while raising the temperature of the cast iron that forms thewalls. The walls and the hotplates radiate an even heat into the ovencavities.

If all five zones were to be switched on simultaneously the total loaddemand would exceed 60 A; therefore the controls limit total currentdemand in some way to a maximum of 30 A. This 30 A limit will allowinstallation of the AGA TC using the normal 6 mm² cooker circuitsavailable in many homes in the UK. The limit is achieved by ‘powersharing’ between elements during heating up periods. The priority for‘power sharing’ between zones follows the zone numbers, i.e. zone 1 hastop priority; zone 2 has second call on power, then zone 3 and so on.

A power de-rating technique is used to maintain the correct temperaturein the hotplates. PID control varies the power to the element as itheats up or cools down from its target temperature.

A more complicated de-rating technique is used to control the cookingperformance of the ovens. Full power is provided until 20° C. belowtarget temperature is achieved; beyond this point electrical power tothe element is limited to a maximum of 20% Top-10% Bottom (2:1 ratio)with PID control varying this between 20% and 0% as the oven temperatureapproaches the target temperature. The Simmering oven has a single 2.5kW element which uses a maximum power level of 50% during warm up andvaries between 25% and 0% during PID control.

The cooker may also include a vent fan to extract moisture and cookingsmells from the oven cavities. The vent fan motor requires a pre-setvariable supply of 12 to 24 v dc, capable of a continuous output of 5 W,provided by an electronic circuit on the main power board. The outputvoltage to the vent fan is set by the installation engineer using apotentiometer situated on the power board.

Once an oven reaches close to it's set point temperature the power dropsto a pre-determined de-rated power, typically 20% (top element) and 10%(bottom element) of full power, preventing aggressive temperature overshoot with in the oven. Once at the desired set point, the temperatureis maintained with PID feed back monitoring and controlled power burstcreating a cycling temperature range of 2° C. The ovens are thereforeheld at the preset temperatures stored in the memory until the ovens areturned off.

The ovens are therefore heated by radiant heat from the cast iron walls,as supplied by the hot plates.

The third part is an optional remote control may be provided whichenables the ovens to be switched on or off remotely. Hand held remotecontrol (HHC) provides the user with timing functions to switch thecooker on and off up to twice a day (Auto modes) and display informationsuch as time/date. The HHC transmits time/event settings via RF to asmall ‘piggyback’ board which stores the Auto programmes. The‘piggyback’ board is connected to the power board via a communicationlink.

The controller can cause the cooker to function in a wide range ofdifferent ways but the following sets out a preferred control logic thatmay be implemented.

If all five zones were to be switched on simultaneously the total loaddemand would exceed 60 A; therefore the controls limit total currentdemand in some way to a maximum of 30 A. This 30 A limit will allowinstallation of the cooker using the normal 6 mm² cooker circuitsavailable in many homes in the UK. The limit is achieved by ‘powersharing’ between elements during heating up periods. The priority for‘power sharing’ between zones follows the zone numbers, i.e. zone 1 hastop priority; zone 2 has second call on power, then zone 3 and so on.

A power de-rating technique is used to maintain the correct temperaturein the hotplates. PID control varies the power to the element as itheats up or cools down from its target temperature.

A more complicated de-rating technique is used to control the cookingperformance of the ovens. Full power is provided until 20° C. belowtarget temperature is achieved; beyond this point electrical power tothe element is limited to a maximum of 20% Top-10% Bottom (2:1 ratio)with PID control varying this between 20% and 0% as the oven temperatureapproaches the target temperature. The Simmering oven has a single 2.5kW element which uses a maximum power level of 50% during warm up andvaries between 25% and 0% during PID control.

The cooker may also include a vent fan to extract moisture and cookingsmells from the oven cavities. The vent fan motor requires a pre-setvariable supply of 12 to 24 v dc, capable of a continuous output of 5 W,provided by an electronic circuit on the main power board. The outputvoltage to the vent fan is set by the installation engineer using apotentiometer situated on the power board.

The user can switch the vent fan on or off manually using a dedicatedvent fan button on the UIB/touch panel.

The user interface board contains piezoelectric touch sensitive switchesor buttons with LED status indication and audible confirmation ofoperation. There are eight switches as shown in FIG. 4 of the drawings.Each switch performs one of the following functions:

-   -   Standby/on    -   Mode—Manual, Slumber, Auto, Auto/Slumber selection    -   Boil (hotspot)—on/off    -   Simmer (simmerspot)—on/off    -   Fan (oven vent fan)—on/off    -   Roast (oven)—on/off or selected for auto    -   Bake (baking oven)—on/off or selected for auto    -   Simmer (oven)—on/off or selected for auto

In addition to these switches the hand held controller can be used tocontrol the cooker. The hand held remote control displays the time, dateand Auto event settings. Programming is via eight push buttons.Information is displayed via a backlit LCD screen. Refer to Appendix 3for screen layouts.

The controller may cause the cooker to operate in one of severaldifferent modes as described hereinafter.

Modes can only be selected or active when the standby button status is‘on’ (green LED). If the standby button status is set to ‘standby’ thenzones cannot be switched on/off or selected/de-selected. ‘Auto’ and‘Auto/Slumber’ mode ‘Events’ will not be activated in ‘standby’ status(indicated by no LED).

Manual—Each zone of the cooker can be operated individually when inmanual mode. The corresponding zone button is pressed once to operate(switch on) and once more to de-select (switch off) the zone. While inmanual mode any zone selected will remain on indefinitely untilde-selected (switched off).

Slumber—In this mode all three oven zones (3, 4 & 5) are active, presetto 120° C., this is termed being in ‘slumber’. No oven zone can be‘off’. Any oven zone can be switched from ‘slumber’ to ‘fulltemperature’ as if in manual mode by one press of the zone button.Pressing the zone button once more returns that zone back to ‘slumber’.

Auto/Slumber—Each of the oven zones, (zones 3, 4 & 5) of the cooker canbe selected to operate once or twice each day, each operation is termedan ‘event’. The start and finish time, and therefore the duration ofeach ‘event’ is chosen by the user. For the time between the ‘events’,the ovens will maintain a temperature of 120° C., this is termed beingin ‘slumber’.

Auto—Each of the oven zones, (zones 3, 4 & 5) of the AGA TC can beselected to operate as in ‘Auto/Slumber’ mode, however during the timebetween ‘events’ the ovens are switched off and allowed to cool.

The five cooking zones are split into two groups, hotplates and ovens.Hotplates (zones 1 & 2) are always manually controlled, while the ovens(zones 3, 4 & 5) can be individually switched ‘on’ in Manual and Slumbermodes or pre-selected to be ‘on’ during ‘event times’ in the Auto modes.There are two ‘Auto’ modes; one can be selected with ‘slumber’ heatingbetween events and the other with no heating between the ‘events’.Selection of the modes is via the ‘Manual, Slumber, Auto, Auto/Slumber’mode button on the UIB/touch panel.

When in either Auto mode, using the handheld remote control, each day ofthe week can be programmed independently for the number of events (0, 1,or 2 events) and each event start/stop time. Oven zones are selected onthe UIB/touch panel and not stored on the remote, so oven selectioncannot be changed within the daily program and the ‘Auto’ zone selectionwill carry over from one day to the next.

When the cooker is under manual operation the following statementsapply:

-   -   The Hand Held Remote Control is not used.    -   Manual mode is selected via the ‘mode’ button on the UIB/touch        panel. Each time the mode button is pressed it steps to the next        mode and indicates the selected mode using one of four LEDs.    -   Each time manual mode is selected all zones are included and are        switched to ‘off’ as a default operation.    -   Once in manual mode each zone can be switched on or off by        pressing the corresponding zone button on the UIB/touch panel.        Confirmation of the button press is by an audible tone, ‘zone        on’ is indicated by the associated zone LED being lit. The zone        LED will flash green while the zone is heating and become        constant when the zone is at or close to operating temperature.    -   Once ‘on’ then each zone will remain ‘on’ indefinitely until        switched ‘off’ using its own zone button or by selection of one        of the other modes using the mode button (when the rules of that        mode will apply to each zone) or by switching the TC to standby.    -   During Manual mode operation any ‘on or off’ event commands from        the auto program are ignored.

When the cooker is in Slumber operation the following statements apply:

-   -   The Hand Held Remote Control is not used.    -   Slumber mode is selected via the ‘Mode’ button on the UIB/touch        panel, each time the button is pressed it steps to the next mode        and indicates the selected mode using one of four LEDs    -   Each time ‘slumber’ mode is selected, all oven zones default to        their respective ‘slumber’ set point (120° C.) this. No oven        zone can be switched ‘off’ from the ‘slumber’ mode.    -   When ‘Slumber’ mode is selected the hotplate zones default to        off.    -   Hotplate zones are not included in ‘slumber’ mode they work as        in ‘Manual’ mode.    -   When in ‘Slumber’ mode any oven zone can be switched from its        ‘slumber temperature’ to ‘full temperature’ by one press of the        zone button, the selected oven setpoint is changed from        ‘slumber’ to ‘full’. The corresponding oven zone button LED        changes colour to indicate which status the zone is in (No LED        for ‘slumber’ mode, green LED for ‘full temperature’).    -   During ‘slumber’ mode operation any ‘on or off’ event commands        from the auto program are ignored.    -   To achieve the slumber set point of 120° C. in the Roast oven        and Baking Oven the same de-rating technique will be used as for        the normal set point i.e. full power is provided until a zone        temperature of 100° C.; beyond this point electrical power to        the element is limited to a maximum of 20% Top-10% Bottom (2:1        ratio) with PID control varying this between 20% and 0% as the        oven temperature approaches the target temperature.

When in Auto operation the following statements apply:

-   -   The Hand Held Remote Control is used to program the Auto        operation.    -   Auto mode is selected via the ‘Mode’ button on the user        interface board; each time the button is pressed it steps to the        next mode and indicates the selected mode using one of four        LEDs.    -   Each time Auto mode is selected all oven zones are switched to        ‘off’ as a default operation unless the real time corresponds        with an ‘event’ time, in which case the selected zones will be        turned on.    -   When ‘Auto’ mode is selected the hotplate zones default to off.    -   Hotplate zones are not included in ‘Auto’ mode, they work as in        ‘Manual’ mode    -   Once in Auto mode each oven zone can be selected or de-selected        for auto operation by pressing the zone button on the UIB/touch        panel.    -   ‘Zone selected’ is indicated by the associated zone LED being        lit yellow. The zone LED will flash green while the oven is        heating and become constant green when the oven is close to        operating temperature during its event period.    -   Once ‘selected’ then each zone will remain ‘selected’        indefinitely until de-selected using its own zone button. The        ‘Auto’ oven zone selection is stored and remembered so that        returning to Auto from non-auto modes (slumber and manual) does        not require resetting of the oven zone selection.    -   During the time between events the ovens are switched off.    -   The ‘events’ are programmed by the handset and are stored by a        ‘piggy back’ board connected to the power board. Confirmation of        receipt of the program settings transmitted from the HHC to the        ‘piggyback board’ is required. (‘message sent ok’ is briefly        displayed on the handset)

When in Auto/Slumber operation the following statements apply:

-   -   The Hand Held Remote Control is used to program the Auto/Slumber        operation.    -   Auto/Slumber mode is selected via the ‘Mode’ button on the        UIB/touch panel; each time the button is pressed it steps to the        next mode and indicates the selected mode using one of four        LEDs.    -   Each time Auto/Slumber mode is selected all oven zones are        switched to ‘slumber’ as a default operation unless the real        time corresponds with an ‘event’ time, in which case the        selected zones will be turned on to ‘full’.    -   When ‘Auto/Slumber’ mode is selected Hotplate zones default to        ‘off’.    -   Hotplates are not included in ‘Auto/Slumber’ mode, they work as        in ‘Manual’ mode    -   Once in Auto/Slumber mode each oven zone can be selected or        de-selected for auto operation by pressing the zone button on        the UIB/touch panel. ‘Zone selected’ is indicated by the        associated zone LED being lit yellow. The zone LED will flash        green while the oven is heating and become constant green when        the oven is close to operating temperature during its event        period    -   Once ‘selected’ then each oven zone will remain ‘selected’        indefinitely until de-selected using its own zone button. The        ‘Auto/Slumber’ oven zone selection is stored and remembered so        that returning to Auto/Slumber from Manual mode does not require        resetting of the oven zone selection.    -   During the time between events the ovens are switched to        Slumber, this means the selected ovens maintain a temperature of        120° C., using the same de-rating techniques as the Slumber mode        set points. The ‘events’ are programmed by the handset and are        stored by a ‘piggy back’ board connected to the power board.        Confirmation of receipt of the program settings transmitted from        the HHC to the ‘piggyback board’ is required.

1. A heat storage cooker comprising at least one oven cavity formed bywalls of cast iron, and at least one electric radiant heating elementwhich is in thermal contact with at least one wall such that in use theelectric radiant heating element transfers heat energy to the wall whichsubsequently radiates at least part of that heat energy into the ovencavity.
 2. The heat storage cooker according to claim 1 in which the atleast one oven cavity includes a radiant hot plate which comprises acast iron body forming a part of the at least one wall and an electricalresistive heating element embedded in the cast iron body.
 3. The heatstorage cooker according to claim 2 in which the radiant hot platecomprises a generally flat plate of ceramic or glass ceramic covering acoil of the electrical resistive heating element.
 4. The heat storagecooker according to claim 1 in which the electric radiant heatingelement is located inside the oven cavity in thermal contact with aninner face of a respective wall.
 5. The heat storage cooker according toclaim 2 in which the electrical resistive heating element is located ina recess in a respective wall of the oven cavity so that the surface ofthe hot plate is substantially flush with the surrounding surface of thewall.
 6. The heat storage cooker according to claim 1 in which two ormore walls are formed as part of a single casting which is in thermalcontact with the electric radiant heating element.
 7. The heat storagecooker according to claim 1 in which a controller is provided whichcontrols the heating of the heating elements.
 8. The heat storage cookeraccording to claim 7 in which two oven cavities are present, each cavityhaving at least one electric radiant heating element which is in thermalcontact with at least one wall to form an integral part of the wall suchthat in use the electric radiant heating element transfers heat energyto the wall which subsequently radiates at least part of that heatenergy into the oven cavity, and the controller includes a setting whichin use causes the heating elements to maintain a first one of the ovensat a first set temperature when the cooker is switched on a second oneof the ovens at a second set temperature when the cooker is switched on,the second set temperature being lower than the first.
 9. The heatstorage cooker according to claim 7 in which the controller is operableto implement the setting at a single command from a user, thetemperatures being stored in a memory associated with the controller.10. The heat storage cooker according to claim 8 in which a third ovencavity is provided which has at least one electric radiant heatingelement which is in thermal contact with at least one wall to form anintegral part of the wall such that in use the electric radiant heatingelement transfers heat energy to the wall which subsequently radiates atleast part of that heat energy into the oven cavity, and the controllersetting in use maintains the third oven at a third set temperature whenthe oven is switched on, the third temperature being different from thefirst and second temperatures.
 11. The heat storage cooker according toclaim 10 in which the three preset temperatures are approximately 240°C., 180° C., and 120° C.
 12. The heat storage cooker according to claim7 in which the controller receives input signals from a thermocoupleassociated with the at least one heating element associated with thecavity, the thermocouple providing an output indicative of thetemperature of the at least one heating element, and also from athermocouple that measures the overall temperature inside an ovencavity.
 13. The heat storage cooker according to any preceding claim 1which is absent any form of central heat source and absent the ductsthat would otherwise be needed to take the heat from a central heatsource to the oven cavity. 14-17. (canceled)
 18. The heat storage cookeraccording to claim 1 which is floor standing and has a width of at least120 cm.
 19. The heat storage cooker according to claim 1 which includesa hob including a hot plate.
 20. The heat storage cooker according toclaim 1, comprising at least two oven cavities, each one formed from aplurality of walls of cast iron and each one being provided with arespective heat source which is adapted to heat the walls of therespective oven cavity which in turn heat the interior of the ovencavity by radiating heat.
 21. The heat storage cooker according to claim20 in which each of the at least two oven cavities is heatedindependently of the other.
 22. The heat storage cooker according toclaim 20 in which each of the at least two oven cavities functionsindependently as a heat storage device wherein the thermal mass of thewalls of the respective oven cavity is sufficient that it retains heatfor an extended period of time to continue to heat the respective ovencavity.
 23. The heat storage cooker according to claim 20 in which theheat source of each of the at least two oven cavities comprises a hotplate or other electrical heating element in thermal contact with atleast one wall of the respective oven cavity.